`clear`ing a dynamic array

[Shriramana Sharma via Digitalmars-d-learn]

Hello. I had first expected that dynamic arrays (slices) would provide a 
`.clear()` method but they don't seem to. Obviously I can always effectively 
clear an array by assigning an empty array to it, but this has unwanted 
consequences that `[]` actually seems to allocate a new dynamic array and 
any other identifiers initially pointing to the same array will still show 
the old contents and thus it would no longer test true for `is` with this 
array. See the following code:

import std.stdio;
void main()
{
  int a[] = [1,2,3,4,5];
  int b[] = a;
  writeln(a);
  writeln(b);
  //a.clear();
  a = [];
  writeln(a);
  writeln(b);
}

which outputs:

[1, 2, 3, 4, 5]
[1, 2, 3, 4, 5]
[]
[1, 2, 3, 4, 5]

How to make it so that after clearing `a`, `b` will also point to the same 
empty array? IOW the desired output is:

[1, 2, 3, 4, 5]
[1, 2, 3, 4, 5]
[]
[]

... and any further items added to `a` should also reflect in `b`. 

-- 
Shriramana Sharma, Penguin #395953